Prevention of biofouling remains a challenging problem in numerous areas. These include, but are not limited to, biomedical applications, marine coating technologies, water filtration, transport, and storage systems. Undesirable consequences of this ubiquitous problem can include reduction in the efficacy/sensitivity of devices, operational losses, thrombosis, as well as microbial infections. Therefore, the development of new technologies and materials that reduce or completely prevent any undesired deposition of microorganisms is of great importance. However, tailoring an efficient non-fouling material requires understanding the interactions involved, which is hindered by the complexity of the process, making it challenging to provide solutions to the problem.
Biofilm formation generally starts within seconds following implantation of a given material (e.g., medical implant) in aqueous environments, such as blood, municipal and/or sea water. While biofilms can be formed by a single species, often they are composed of a community of different types of microorganisms. The first step of the process is often the adsorption of proteins on the substrate surface, which is followed by adsorption of a cascade of larger, more complex species that include microorganisms such as bacteria, fungi, and algae. Thus, one can argue that the larger microorganisms rarely interact with the clean surface but rather with the proteins adsorbed on it. One approach that has been employed to prevent the biofoulmg process is the incorporation of antimicrobially active ingredients into materials. This can be done by blending actives into the material during its manufacture, covalently attaching an active agent to the surface of the material, or coating/painting an antimicrobial onto a surface such that it can subsequently leach from the material. However, once a certain amount of organic material (e.g., cell debris) has formed, the surface activity decreases as the active material can no longer reach its target. An alternative approach is to prevent biofoulmg by preventing the attachment of a broad range of species, rather than killing them.
A key challenge in preventing biofilm formation is the design of smart materials or engineered surfaces that can effectively resist the irreversible attachment of a wide variety of species including proteins, microbial cells, and spores. Many approaches have been investigated, and hydrophilic modification of surfaces using polyethylene glycol) (PEG) and zwitterionic polymers with high wettability are among the most promising. However, larger microorganisms as well as proteins are inherently amphiphilic. They operate by different attachment mechanisms, with some having higher attachment affinity to hydrophobic surfaces and others to hydrophilic surfaces. Therefore, a desirable antifouling coating can be defined as one that can show stealth behavior against multiple species. With these findings, there is increasing demand for engineered materials, particularly amphiphilic materials, which, similar to living organisms, can restructure their surfaces depending on the environment. However, one should be aware that a delicate balance of hydrophilicity to hydrophobicity (or amphiphilicity) should be met for a particular surface/coating to be effective in prevention of biofilm formation across a wide variety of species.